The present invention relates to a press for manufacturing helical gears.
When manufacturing helical gears, the prior art has in general machined blanks by means of a hob cutter or a pinion cutter, and added, as required, a post-process of a gear shaving or gear grinding. However, this is a pure machining process which forms gears by producing chips bit by bit, and therefore it has shortcomings of low efficiency and high production cost.
As an alternative to the gear machining process, a plastic working process has been practised for making gears. Typical examples are a cold and hot rolling process and a cold and hot forging process, which have good productivity and are advantageous in producing no chips but have drawbacks as mentioned below, and so are not always practical in a helical gear making process.
The rolling process requires an expensive machine, and since this process urges a material circumferentially thereof so as to swell it up, it is difficult to divide the circumference of the material into teeth of a determined number and it is not possible to create a tooth shape that has a large height. In addition, when manufacturing gears having axial holes, the hole is deformed by rolling pressure.
On the other hand, the forging process must effect plastic flow over the whole of gear material, so that the processing force is very large and a pressing machine must be scaled large accordingly so that a procedure must be carried out at a relatively high level to in order to design and produce a sample. Thus, the cost is high as a whole.